Networking work-in-progress:

As per work done by szisti in PR#45:
Extracted MessageException from inside Message into its own class.
Extracted MessageType from inside Message into its own class.

Converted reflection-based Message.fromByteBuffer method call to non-reflection, functional interface, method-reference.
This should have minor performance improvement but stronger method signature and type enforcement, as well as better IDE integration.

Message.fromByteBuffer method 'contract' tightened up to:
1. throw BufferUnderflowException if there are not enough bytes to deserialize message
2. throw MessageException if bytes contain invalid data
3. should not return null

Message.toData method 'contract' tightened up to:
1. return null if the message has no payload to serialize
2. throw IOException directly - no need to try-catch in each subclass

Several Message-subclass fields now marked 'final' as per IDE suggestion.
Several Message-subclass fromByteBuffer() method signatures have changed 'throws' list.
Several bytes.remaining() != some-value changed to bytes.remaining() < some-value as per new contract.

Some bytes.remaining() checks removed for fixed-length messages because we can rely on ByteBuffer throwing BufferUnderflowException.
Some bytes.remaining() checks retained for variable-length messages, or messages that read a large amount of data, to prevent wasted memory allocations.

Other minor tidying up

src/main/java/org/qortal/controller/Synchronizer.java

@@ -33,7 +33,7 @@ import org.qortal.network.message.GetBlockSummariesMessage;
 import org.qortal.network.message.GetSignaturesV2Message;
 import org.qortal.network.message.Message;
 import org.qortal.network.message.SignaturesMessage;
-import org.qortal.network.message.Message.MessageType;
+import org.qortal.network.message.MessageType;
 import org.qortal.repository.DataException;
 import org.qortal.repository.Repository;
 import org.qortal.repository.RepositoryManager;

src/main/java/org/qortal/controller/arbitrary/ArbitraryDataFileManager.java

@@ -7,7 +7,6 @@ import org.qortal.controller.Controller;
 import org.qortal.data.arbitrary.ArbitraryDirectConnectionInfo;
 import org.qortal.data.arbitrary.ArbitraryFileListResponseInfo;
 import org.qortal.data.arbitrary.ArbitraryRelayInfo;
-import org.qortal.data.network.ArbitraryPeerData;
 import org.qortal.data.network.PeerData;
 import org.qortal.data.transaction.ArbitraryTransactionData;
 import org.qortal.network.Network;
@@ -210,7 +209,7 @@ public class ArbitraryDataFileManager extends Thread {
                 LOGGER.debug("Received null message from peer {}", peer);
                 return null;
             }
-            if (message.getType() != Message.MessageType.ARBITRARY_DATA_FILE) {
+            if (message.getType() != MessageType.ARBITRARY_DATA_FILE) {
                 LOGGER.debug("Received message with invalid type: {} from peer {}", message.getType(), peer);
                 return null;
             }

src/main/java/org/qortal/network/Handshake.java

@@ -13,7 +13,7 @@ import org.qortal.crypto.MemoryPoW;
 import org.qortal.network.message.ChallengeMessage;
 import org.qortal.network.message.HelloMessage;
 import org.qortal.network.message.Message;
-import org.qortal.network.message.Message.MessageType;
+import org.qortal.network.message.MessageType;
 import org.qortal.settings.Settings;
 import org.qortal.network.message.ResponseMessage;
 import org.qortal.utils.DaemonThreadFactory;

src/main/java/org/qortal/network/Peer.java

@@ -11,8 +11,8 @@ import org.qortal.data.network.PeerChainTipData;
 import org.qortal.data.network.PeerData;
 import org.qortal.network.message.ChallengeMessage;
 import org.qortal.network.message.Message;
-import org.qortal.network.message.Message.MessageException;
-import org.qortal.network.message.Message.MessageType;
+import org.qortal.network.message.MessageException;
+import org.qortal.network.message.MessageType;
 import org.qortal.network.message.PingMessage;
 import org.qortal.settings.Settings;
 import org.qortal.utils.ExecuteProduceConsume;

src/main/java/org/qortal/network/message/ArbitraryDataFileListMessage.java

@@ -9,17 +9,12 @@ import org.qortal.utils.Serialization;
 
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
-import java.io.UnsupportedEncodingException;
 import java.nio.ByteBuffer;
 import java.util.ArrayList;
 import java.util.List;
 
 public class ArbitraryDataFileListMessage extends Message {
 
-	private static final int SIGNATURE_LENGTH = Transformer.SIGNATURE_LENGTH;
-	private static final int HASH_LENGTH = Transformer.SHA256_LENGTH;
-	private static final int MAX_PEER_ADDRESS_LENGTH = PeerData.MAX_PEER_ADDRESS_SIZE;
-
 	private final byte[] signature;
 	private final List<byte[]> hashes;
 	private Long requestTime;
@@ -60,16 +55,15 @@ public class ArbitraryDataFileListMessage extends Message {
 		return this.signature;
 	}
 
-	public static Message fromByteBuffer(int id, ByteBuffer bytes) throws UnsupportedEncodingException, TransformationException {
-		byte[] signature = new byte[SIGNATURE_LENGTH];
+	public static Message fromByteBuffer(int id, ByteBuffer bytes) throws MessageException {
+		byte[] signature = new byte[Transformer.SIGNATURE_LENGTH];
 		bytes.get(signature);
 
 		int count = bytes.getInt();
 
 		List<byte[]> hashes = new ArrayList<>();
 		for (int i = 0; i < count; ++i) {
-
-			byte[] hash = new byte[HASH_LENGTH];
+			byte[] hash = new byte[Transformer.SHA256_LENGTH];
 			bytes.get(hash);
 			hashes.add(hash);
 		}
@@ -82,51 +76,49 @@ public class ArbitraryDataFileListMessage extends Message {
 		// The remaining fields are optional
 
 		if (bytes.hasRemaining()) {
+			try {
+				requestTime = bytes.getLong();
 
-			requestTime = bytes.getLong();
+				requestHops = bytes.getInt();
 
-			requestHops = bytes.getInt();
-
-			peerAddress = Serialization.deserializeSizedStringV2(bytes, MAX_PEER_ADDRESS_LENGTH);
-
-			isRelayPossible = bytes.getInt() > 0;
+				peerAddress = Serialization.deserializeSizedStringV2(bytes, PeerData.MAX_PEER_ADDRESS_SIZE);
 
+				isRelayPossible = bytes.getInt() > 0;
+			} catch (TransformationException e) {
+				throw new MessageException(e.getMessage(), e);
+			}
 		}
 
 		return new ArbitraryDataFileListMessage(id, signature, hashes, requestTime, requestHops, peerAddress, isRelayPossible);
 	}
 
 	@Override
-	protected byte[] toData() {
-		try {
-			ByteArrayOutputStream bytes = new ByteArrayOutputStream();
+	protected byte[] toData() throws IOException {
+		ByteArrayOutputStream bytes = new ByteArrayOutputStream();
 
-			bytes.write(this.signature);
+		bytes.write(this.signature);
 
-			bytes.write(Ints.toByteArray(this.hashes.size()));
+		bytes.write(Ints.toByteArray(this.hashes.size()));
 
-			for (byte[] hash : this.hashes) {
-				bytes.write(hash);
-			}
-
-			if (this.requestTime == null) { // To maintain backwards support
-				return bytes.toByteArray();
-			}
-
-			// The remaining fields are optional
-
-			bytes.write(Longs.toByteArray(this.requestTime));
-
-			bytes.write(Ints.toByteArray(this.requestHops));
-
-			Serialization.serializeSizedStringV2(bytes, this.peerAddress);
-
-			bytes.write(Ints.toByteArray(this.isRelayPossible ? 1 : 0));
-
-			return bytes.toByteArray();
-		} catch (IOException e) {
-			return null;
+		for (byte[] hash : this.hashes) {
+			bytes.write(hash);
 		}
+
+		if (this.requestTime == null) { // To maintain backwards support
+			return bytes.toByteArray();
+		}
+
+		// The remaining fields are optional
+
+		bytes.write(Longs.toByteArray(this.requestTime));
+
+		bytes.write(Ints.toByteArray(this.requestHops));
+
+		Serialization.serializeSizedStringV2(bytes, this.peerAddress);
+
+		bytes.write(Ints.toByteArray(this.isRelayPossible ? 1 : 0));
+
+		return bytes.toByteArray();
 	}
 
 	public ArbitraryDataFileListMessage cloneWithNewId(int newId) {

src/main/java/org/qortal/network/message/ArbitraryDataFileMessage.java

@@ -9,15 +9,13 @@ import org.qortal.transform.Transformer;
 
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
-import java.io.UnsupportedEncodingException;
+import java.nio.BufferUnderflowException;
 import java.nio.ByteBuffer;
 
 public class ArbitraryDataFileMessage extends Message {
 
 	private static final Logger LOGGER = LogManager.getLogger(ArbitraryDataFileMessage.class);
 
-	private static final int SIGNATURE_LENGTH = Transformer.SIGNATURE_LENGTH;
-
 	private final byte[] signature;
 	private final ArbitraryDataFile arbitraryDataFile;
 
@@ -39,14 +37,14 @@ public class ArbitraryDataFileMessage extends Message {
 		return this.arbitraryDataFile;
 	}
 
-	public static Message fromByteBuffer(int id, ByteBuffer byteBuffer) throws UnsupportedEncodingException {
-		byte[] signature = new byte[SIGNATURE_LENGTH];
+	public static Message fromByteBuffer(int id, ByteBuffer byteBuffer) throws MessageException {
+		byte[] signature = new byte[Transformer.SIGNATURE_LENGTH];
 		byteBuffer.get(signature);
 
 		int dataLength = byteBuffer.getInt();
 
-		if (byteBuffer.remaining() != dataLength)
-			return null;
+		if (byteBuffer.remaining() < dataLength)
+			throw new BufferUnderflowException();
 
 		byte[] data = new byte[dataLength];
 		byteBuffer.get(data);
@@ -54,15 +52,14 @@ public class ArbitraryDataFileMessage extends Message {
 		try {
 			ArbitraryDataFile arbitraryDataFile = new ArbitraryDataFile(data, signature);
 			return new ArbitraryDataFileMessage(id, signature, arbitraryDataFile);
-		}
-		catch (DataException e) {
+		} catch (DataException e) {
 			LOGGER.info("Unable to process received file: {}", e.getMessage());
-			return null;
+			throw new MessageException("Unable to process received file: " + e.getMessage(), e);
 		}
 	}
 
 	@Override
-	protected byte[] toData() {
+	protected byte[] toData() throws IOException {
 		if (this.arbitraryDataFile == null) {
 			return null;
 		}
@@ -72,19 +69,15 @@ public class ArbitraryDataFileMessage extends Message {
 			return null;
 		}
 
-		try {
-			ByteArrayOutputStream bytes = new ByteArrayOutputStream();
+		ByteArrayOutputStream bytes = new ByteArrayOutputStream();
 
-			bytes.write(signature);
+		bytes.write(signature);
 
-			bytes.write(Ints.toByteArray(data.length));
+		bytes.write(Ints.toByteArray(data.length));
 
-			bytes.write(data);
+		bytes.write(data);
 
-			return bytes.toByteArray();
-		} catch (IOException e) {
-			return null;
-		}
+		return bytes.toByteArray();
 	}
 
 	public ArbitraryDataFileMessage cloneWithNewId(int newId) {

src/main/java/org/qortal/network/message/ArbitraryDataMessage.java

@@ -2,7 +2,7 @@ package org.qortal.network.message;
 
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
-import java.io.UnsupportedEncodingException;
+import java.nio.BufferUnderflowException;
 import java.nio.ByteBuffer;
 
 import org.qortal.transform.Transformer;
@@ -11,10 +11,8 @@ import com.google.common.primitives.Ints;
 
 public class ArbitraryDataMessage extends Message {
 
-	private static final int SIGNATURE_LENGTH = Transformer.SIGNATURE_LENGTH;
-
-	private byte[] signature;
-	private byte[] data;
+	private final byte[] signature;
+	private final byte[] data;
 
 	public ArbitraryDataMessage(byte[] signature, byte[] data) {
 		this(-1, signature, data);
@@ -35,14 +33,14 @@ public class ArbitraryDataMessage extends Message {
 		return this.data;
 	}
 
-	public static Message fromByteBuffer(int id, ByteBuffer byteBuffer) throws UnsupportedEncodingException {
-		byte[] signature = new byte[SIGNATURE_LENGTH];
+	public static Message fromByteBuffer(int id, ByteBuffer byteBuffer) {
+		byte[] signature = new byte[Transformer.SIGNATURE_LENGTH];
 		byteBuffer.get(signature);
 
 		int dataLength = byteBuffer.getInt();
 
-		if (byteBuffer.remaining() != dataLength)
-			return null;
+		if (byteBuffer.remaining() < dataLength)
+			throw new BufferUnderflowException();
 
 		byte[] data = new byte[dataLength];
 		byteBuffer.get(data);
@@ -51,23 +49,19 @@ public class ArbitraryDataMessage extends Message {
 	}
 
 	@Override
-	protected byte[] toData() {
+	protected byte[] toData() throws IOException {
 		if (this.data == null)
 			return null;
 
-		try {
-			ByteArrayOutputStream bytes = new ByteArrayOutputStream();
+		ByteArrayOutputStream bytes = new ByteArrayOutputStream();
 
-			bytes.write(this.signature);
+		bytes.write(this.signature);
 
-			bytes.write(Ints.toByteArray(this.data.length));
+		bytes.write(Ints.toByteArray(this.data.length));
 
-			bytes.write(this.data);
+		bytes.write(this.data);
 
-			return bytes.toByteArray();
-		} catch (IOException e) {
-			return null;
-		}
+		return bytes.toByteArray();
 	}
 
 }

src/main/java/org/qortal/network/message/ArbitraryMetadataMessage.java

@@ -7,13 +7,11 @@ import org.qortal.transform.Transformer;
 
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
-import java.io.UnsupportedEncodingException;
+import java.nio.BufferUnderflowException;
 import java.nio.ByteBuffer;
 
 public class ArbitraryMetadataMessage extends Message {
 
-	private static final int SIGNATURE_LENGTH = Transformer.SIGNATURE_LENGTH;
-
 	private final byte[] signature;
 	private final ArbitraryDataFile arbitraryMetadataFile;
 
@@ -39,14 +37,14 @@ public class ArbitraryMetadataMessage extends Message {
 		return this.arbitraryMetadataFile;
 	}
 
-	public static Message fromByteBuffer(int id, ByteBuffer byteBuffer) throws UnsupportedEncodingException {
-		byte[] signature = new byte[SIGNATURE_LENGTH];
+	public static Message fromByteBuffer(int id, ByteBuffer byteBuffer) throws MessageException {
+		byte[] signature = new byte[Transformer.SIGNATURE_LENGTH];
 		byteBuffer.get(signature);
 
 		int dataLength = byteBuffer.getInt();
 
-		if (byteBuffer.remaining() != dataLength)
-			return null;
+		if (byteBuffer.remaining() < dataLength)
+			throw new BufferUnderflowException();
 
 		byte[] data = new byte[dataLength];
 		byteBuffer.get(data);
@@ -54,14 +52,13 @@ public class ArbitraryMetadataMessage extends Message {
 		try {
 			ArbitraryDataFile arbitraryMetadataFile = new ArbitraryDataFile(data, signature);
 			return new ArbitraryMetadataMessage(id, signature, arbitraryMetadataFile);
-		}
-		catch (DataException e) {
-			return null;
+		} catch (DataException e) {
+			throw new MessageException("Unable to process arbitrary metadata message: " + e.getMessage(), e);
 		}
 	}
 
 	@Override
-	protected byte[] toData() {
+	protected byte[] toData() throws IOException {
 		if (this.arbitraryMetadataFile == null) {
 			return null;
 		}
@@ -71,19 +68,15 @@ public class ArbitraryMetadataMessage extends Message {
 			return null;
 		}
 
-		try {
-			ByteArrayOutputStream bytes = new ByteArrayOutputStream();
+		ByteArrayOutputStream bytes = new ByteArrayOutputStream();
 
-			bytes.write(signature);
+		bytes.write(signature);
 
-			bytes.write(Ints.toByteArray(data.length));
+		bytes.write(Ints.toByteArray(data.length));
 
-			bytes.write(data);
+		bytes.write(data);
 
-			return bytes.toByteArray();
-		} catch (IOException e) {
-			return null;
-		}
+		return bytes.toByteArray();
 	}
 
 	public ArbitraryMetadataMessage cloneWithNewId(int newId) {

src/main/java/org/qortal/network/message/ArbitrarySignaturesMessage.java

@@ -8,15 +8,13 @@ import org.qortal.utils.Serialization;
 
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
-import java.io.UnsupportedEncodingException;
+import java.nio.BufferUnderflowException;
 import java.nio.ByteBuffer;
 import java.util.ArrayList;
 import java.util.List;
 
 public class ArbitrarySignaturesMessage extends Message {
 
-	private static final int SIGNATURE_LENGTH = Transformer.SIGNATURE_LENGTH;
-
 	private String peerAddress;
 	private int requestHops;
 	private List<byte[]> signatures;
@@ -49,19 +47,24 @@ public class ArbitrarySignaturesMessage extends Message {
 		this.requestHops = requestHops;
 	}
 
-	public static Message fromByteBuffer(int id, ByteBuffer bytes) throws UnsupportedEncodingException, TransformationException {
-		String peerAddress = Serialization.deserializeSizedStringV2(bytes, PeerData.MAX_PEER_ADDRESS_SIZE);
+	public static Message fromByteBuffer(int id, ByteBuffer bytes) throws MessageException {
+		String peerAddress;
+		try {
+			peerAddress = Serialization.deserializeSizedStringV2(bytes, PeerData.MAX_PEER_ADDRESS_SIZE);
+		} catch (TransformationException e) {
+			throw new MessageException(e.getMessage(), e);
+		}
 
 		int requestHops = bytes.getInt();
 
 		int signatureCount = bytes.getInt();
 
-		if (bytes.remaining() != signatureCount * SIGNATURE_LENGTH)
-			return null;
+		if (bytes.remaining() < signatureCount * Transformer.SIGNATURE_LENGTH)
+			throw new BufferUnderflowException();
 
 		List<byte[]> signatures = new ArrayList<>();
 		for (int i = 0; i < signatureCount; ++i) {
-			byte[] signature = new byte[SIGNATURE_LENGTH];
+			byte[] signature = new byte[Transformer.SIGNATURE_LENGTH];
 			bytes.get(signature);
 			signatures.add(signature);
 		}
@@ -70,23 +73,19 @@ public class ArbitrarySignaturesMessage extends Message {
 	}
 
 	@Override
-	protected byte[] toData() {
-		try {
-			ByteArrayOutputStream bytes = new ByteArrayOutputStream();
+	protected byte[] toData() throws IOException {
+		ByteArrayOutputStream bytes = new ByteArrayOutputStream();
 
-			Serialization.serializeSizedStringV2(bytes, this.peerAddress);
+		Serialization.serializeSizedStringV2(bytes, this.peerAddress);
 
-			bytes.write(Ints.toByteArray(this.requestHops));
+		bytes.write(Ints.toByteArray(this.requestHops));
 
-			bytes.write(Ints.toByteArray(this.signatures.size()));
+		bytes.write(Ints.toByteArray(this.signatures.size()));
 
-			for (byte[] signature : this.signatures)
-				bytes.write(signature);
+		for (byte[] signature : this.signatures)
+			bytes.write(signature);
 
-			return bytes.toByteArray();
-		} catch (IOException e) {
-			return null;
-		}
+		return bytes.toByteArray();
 	}
 
 }

src/main/java/org/qortal/network/message/BlockMessage.java

@@ -2,7 +2,6 @@ package org.qortal.network.message;
 
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
-import java.io.UnsupportedEncodingException;
 import java.nio.ByteBuffer;
 import java.util.List;
 
@@ -28,7 +27,7 @@ public class BlockMessage extends Message {
 	private List<TransactionData> transactions = null;
 	private List<ATStateData> atStates = null;
 
-	private int height;
+	private final int height;
 
 	public BlockMessage(Block block) {
 		super(MessageType.BLOCK);
@@ -60,7 +59,7 @@ public class BlockMessage extends Message {
 		return this.atStates;
 	}
 
-	public static Message fromByteBuffer(int id, ByteBuffer byteBuffer) throws UnsupportedEncodingException {
+	public static Message fromByteBuffer(int id, ByteBuffer byteBuffer) throws MessageException {
 		try {
 			int height = byteBuffer.getInt();
 
@@ -72,26 +71,22 @@ public class BlockMessage extends Message {
 			return new BlockMessage(id, blockData, blockInfo.getB(), blockInfo.getC());
 		} catch (TransformationException e) {
 			LOGGER.info(String.format("Received garbled BLOCK message: %s", e.getMessage()));
-			return null;
+			throw new MessageException(e.getMessage(), e);
 		}
 	}
 
 	@Override
-	protected byte[] toData() {
+	protected byte[] toData() throws IOException, TransformationException {
 		if (this.block == null)
 			return null;
 
-		try {
-			ByteArrayOutputStream bytes = new ByteArrayOutputStream();
+		ByteArrayOutputStream bytes = new ByteArrayOutputStream();
 
-			bytes.write(Ints.toByteArray(this.height));
+		bytes.write(Ints.toByteArray(this.height));
 
-			bytes.write(BlockTransformer.toBytes(this.block));
+		bytes.write(BlockTransformer.toBytes(this.block));
 
-			return bytes.toByteArray();
-		} catch (TransformationException | IOException e) {
-			return null;
-		}
+		return bytes.toByteArray();
 	}
 
 	public BlockMessage cloneWithNewId(int newId) {

src/main/java/org/qortal/network/message/BlockSummariesMessage.java

@@ -2,7 +2,7 @@ package org.qortal.network.message;
 
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
-import java.io.UnsupportedEncodingException;
+import java.nio.BufferUnderflowException;
 import java.nio.ByteBuffer;
 import java.util.ArrayList;
 import java.util.List;
@@ -17,7 +17,7 @@ public class BlockSummariesMessage extends Message {
 
 	private static final int BLOCK_SUMMARY_LENGTH = BlockTransformer.BLOCK_SIGNATURE_LENGTH + Transformer.INT_LENGTH + Transformer.PUBLIC_KEY_LENGTH + Transformer.INT_LENGTH;
 
-	private List<BlockSummaryData> blockSummaries;
+	private final List<BlockSummaryData> blockSummaries;
 
 	public BlockSummariesMessage(List<BlockSummaryData> blockSummaries) {
 		this(-1, blockSummaries);
@@ -33,11 +33,11 @@ public class BlockSummariesMessage extends Message {
 		return this.blockSummaries;
 	}
 
-	public static Message fromByteBuffer(int id, ByteBuffer bytes) throws UnsupportedEncodingException {
+	public static Message fromByteBuffer(int id, ByteBuffer bytes) {
 		int count = bytes.getInt();
 
-		if (bytes.remaining() != count * BLOCK_SUMMARY_LENGTH)
-			return null;
+		if (bytes.remaining() < count * BLOCK_SUMMARY_LENGTH)
+			throw new BufferUnderflowException();
 
 		List<BlockSummaryData> blockSummaries = new ArrayList<>();
 		for (int i = 0; i < count; ++i) {
@@ -59,23 +59,19 @@ public class BlockSummariesMessage extends Message {
 	}
 
 	@Override
-	protected byte[] toData() {
-		try {
-			ByteArrayOutputStream bytes = new ByteArrayOutputStream();
+	protected byte[] toData() throws IOException {
+		ByteArrayOutputStream bytes = new ByteArrayOutputStream();
 
-			bytes.write(Ints.toByteArray(this.blockSummaries.size()));
+		bytes.write(Ints.toByteArray(this.blockSummaries.size()));
 
-			for (BlockSummaryData blockSummary : this.blockSummaries) {
-				bytes.write(Ints.toByteArray(blockSummary.getHeight()));
-				bytes.write(blockSummary.getSignature());
-				bytes.write(blockSummary.getMinterPublicKey());
-				bytes.write(Ints.toByteArray(blockSummary.getOnlineAccountsCount()));
-			}
-
-			return bytes.toByteArray();
-		} catch (IOException e) {
-			return null;
+		for (BlockSummaryData blockSummary : this.blockSummaries) {
+			bytes.write(Ints.toByteArray(blockSummary.getHeight()));
+			bytes.write(blockSummary.getSignature());
+			bytes.write(blockSummary.getMinterPublicKey());
+			bytes.write(Ints.toByteArray(blockSummary.getOnlineAccountsCount()));
 		}
+
+		return bytes.toByteArray();
 	}
 
 }

src/main/java/org/qortal/network/message/CachedBlockMessage.java

@@ -2,7 +2,6 @@ package org.qortal.network.message;
 
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
-import java.io.UnsupportedEncodingException;
 import java.nio.ByteBuffer;
 
 import org.qortal.block.Block;
@@ -14,7 +13,7 @@ import com.google.common.primitives.Ints;
 // This is an OUTGOING-only Message which more readily lends itself to being cached
 public class CachedBlockMessage extends Message {
 
-	private Block block = null;
+	private Block block;
 	private byte[] cachedBytes = null;
 
 	public CachedBlockMessage(Block block) {
@@ -30,12 +29,12 @@ public class CachedBlockMessage extends Message {
 		this.cachedBytes = cachedBytes;
 	}
 	
-	public static Message fromByteBuffer(int id, ByteBuffer byteBuffer) throws UnsupportedEncodingException {
+	public static Message fromByteBuffer(int id, ByteBuffer byteBuffer) {
 		throw new UnsupportedOperationException("CachedBlockMessage is for outgoing messages only");
 	}
 
 	@Override
-	protected byte[] toData() {
+	protected byte[] toData() throws IOException, TransformationException {
 		// Already serialized?
 		if (this.cachedBytes != null)
 			return cachedBytes;
@@ -43,22 +42,18 @@ public class CachedBlockMessage extends Message {
 		if (this.block == null)
 			return null;
 
-		try {
-			ByteArrayOutputStream bytes = new ByteArrayOutputStream();
+		ByteArrayOutputStream bytes = new ByteArrayOutputStream();
 
-			bytes.write(Ints.toByteArray(this.block.getBlockData().getHeight()));
+		bytes.write(Ints.toByteArray(this.block.getBlockData().getHeight()));
 
-			bytes.write(BlockTransformer.toBytes(this.block));
+		bytes.write(BlockTransformer.toBytes(this.block));
 
-			this.cachedBytes = bytes.toByteArray();
-			// We no longer need source Block
-			// and Block contains repository handle which is highly likely to be invalid after this call
-			this.block = null;
+		this.cachedBytes = bytes.toByteArray();
+		// We no longer need source Block
+		// and Block contains repository handle which is highly likely to be invalid after this call
+		this.block = null;
 
-			return this.cachedBytes;
-		} catch (TransformationException | IOException e) {
-			return null;
-		}
+		return this.cachedBytes;
 	}
 
 	public CachedBlockMessage cloneWithNewId(int newId) {

src/main/java/org/qortal/network/message/GetArbitraryDataFileListMessage.java

@@ -5,25 +5,16 @@ import com.google.common.primitives.Longs;
 import org.qortal.data.network.PeerData;
 import org.qortal.transform.TransformationException;
 import org.qortal.transform.Transformer;
-import org.qortal.transform.transaction.TransactionTransformer;
 import org.qortal.utils.Serialization;
 
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
-import java.io.UnsupportedEncodingException;
 import java.nio.ByteBuffer;
 import java.util.ArrayList;
 import java.util.List;
 
-import static org.qortal.transform.Transformer.INT_LENGTH;
-import static org.qortal.transform.Transformer.LONG_LENGTH;
-
 public class GetArbitraryDataFileListMessage extends Message {
 
-	private static final int SIGNATURE_LENGTH = Transformer.SIGNATURE_LENGTH;
-	private static final int HASH_LENGTH = TransactionTransformer.SHA256_LENGTH;
-	private static final int MAX_PEER_ADDRESS_LENGTH = PeerData.MAX_PEER_ADDRESS_SIZE;
-
 	private final byte[] signature;
 	private List<byte[]> hashes;
 	private final long requestTime;
@@ -52,8 +43,8 @@ public class GetArbitraryDataFileListMessage extends Message {
 		return this.hashes;
 	}
 
-	public static Message fromByteBuffer(int id, ByteBuffer bytes) throws UnsupportedEncodingException, TransformationException {
-		byte[] signature = new byte[SIGNATURE_LENGTH];
+	public static Message fromByteBuffer(int id, ByteBuffer bytes) throws MessageException {
+		byte[] signature = new byte[Transformer.SIGNATURE_LENGTH];
 
 		bytes.get(signature);
 
@@ -67,7 +58,7 @@ public class GetArbitraryDataFileListMessage extends Message {
 
 			hashes = new ArrayList<>();
 			for (int i = 0; i < hashCount; ++i) {
-				byte[] hash = new byte[HASH_LENGTH];
+				byte[] hash = new byte[Transformer.SHA256_LENGTH];
 				bytes.get(hash);
 				hashes.add(hash);
 			}
@@ -75,42 +66,42 @@ public class GetArbitraryDataFileListMessage extends Message {
 
 		String requestingPeer = null;
 		if (bytes.hasRemaining()) {
-			requestingPeer = Serialization.deserializeSizedStringV2(bytes, MAX_PEER_ADDRESS_LENGTH);
+			try {
+				requestingPeer = Serialization.deserializeSizedStringV2(bytes, PeerData.MAX_PEER_ADDRESS_SIZE);
+			} catch (TransformationException e) {
+				throw new MessageException(e.getMessage(), e);
+			}
 		}
 
 		return new GetArbitraryDataFileListMessage(id, signature, hashes, requestTime, requestHops, requestingPeer);
 	}
 
 	@Override
-	protected byte[] toData() {
-		try {
-			ByteArrayOutputStream bytes = new ByteArrayOutputStream();
+	protected byte[] toData() throws IOException {
+		ByteArrayOutputStream bytes = new ByteArrayOutputStream();
 
-			bytes.write(this.signature);
+		bytes.write(this.signature);
 
-			bytes.write(Longs.toByteArray(this.requestTime));
+		bytes.write(Longs.toByteArray(this.requestTime));
 
-			bytes.write(Ints.toByteArray(this.requestHops));
+		bytes.write(Ints.toByteArray(this.requestHops));
 
-			if (this.hashes != null) {
-				bytes.write(Ints.toByteArray(this.hashes.size()));
+		if (this.hashes != null) {
+			bytes.write(Ints.toByteArray(this.hashes.size()));
 
-				for (byte[] hash : this.hashes) {
-					bytes.write(hash);
-				}
+			for (byte[] hash : this.hashes) {
+				bytes.write(hash);
 			}
-			else {
-				bytes.write(Ints.toByteArray(0));
-			}
-
-			if (this.requestingPeer != null) {
-				Serialization.serializeSizedStringV2(bytes, this.requestingPeer);
-			}
-
-			return bytes.toByteArray();
-		} catch (IOException e) {
-			return null;
 		}
+		else {
+			bytes.write(Ints.toByteArray(0));
+		}
+
+		if (this.requestingPeer != null) {
+			Serialization.serializeSizedStringV2(bytes, this.requestingPeer);
+		}
+
+		return bytes.toByteArray();
 	}
 
 	public long getRequestTime() {

src/main/java/org/qortal/network/message/GetArbitraryDataFileMessage.java

@@ -1,18 +1,13 @@
 package org.qortal.network.message;
 
 import org.qortal.transform.Transformer;
-import org.qortal.transform.transaction.TransactionTransformer;
 
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
-import java.io.UnsupportedEncodingException;
 import java.nio.ByteBuffer;
 
 public class GetArbitraryDataFileMessage extends Message {
 
-	private static final int SIGNATURE_LENGTH = Transformer.SIGNATURE_LENGTH;
-	private static final int HASH_LENGTH = TransactionTransformer.SHA256_LENGTH;
-
 	private final byte[] signature;
 	private final byte[] hash;
 
@@ -35,32 +30,25 @@ public class GetArbitraryDataFileMessage extends Message {
 		return this.hash;
 	}
 
-	public static Message fromByteBuffer(int id, ByteBuffer bytes) throws UnsupportedEncodingException {
-		if (bytes.remaining() != HASH_LENGTH + SIGNATURE_LENGTH)
-			return null;
-
-		byte[] signature = new byte[SIGNATURE_LENGTH];
+	public static Message fromByteBuffer(int id, ByteBuffer bytes) {
+		byte[] signature = new byte[Transformer.SIGNATURE_LENGTH];
 		bytes.get(signature);
 
-		byte[] hash = new byte[HASH_LENGTH];
+		byte[] hash = new byte[Transformer.SHA256_LENGTH];
 		bytes.get(hash);
 
 		return new GetArbitraryDataFileMessage(id, signature, hash);
 	}
 
 	@Override
-	protected byte[] toData() {
-		try {
-			ByteArrayOutputStream bytes = new ByteArrayOutputStream();
+	protected byte[] toData() throws IOException {
+		ByteArrayOutputStream bytes = new ByteArrayOutputStream();
 
-			bytes.write(this.signature);
+		bytes.write(this.signature);
 
-			bytes.write(this.hash);
+		bytes.write(this.hash);
 
-			return bytes.toByteArray();
-		} catch (IOException e) {
-			return null;
-		}
+		return bytes.toByteArray();
 	}
 
 }

src/main/java/org/qortal/network/message/GetArbitraryDataMessage.java

@@ -2,16 +2,13 @@ package org.qortal.network.message;
 
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
-import java.io.UnsupportedEncodingException;
 import java.nio.ByteBuffer;
 
 import org.qortal.transform.Transformer;
 
 public class GetArbitraryDataMessage extends Message {
 
-	private static final int SIGNATURE_LENGTH = Transformer.SIGNATURE_LENGTH;
-
-	private byte[] signature;
+	private final byte[] signature;
 
 	public GetArbitraryDataMessage(byte[] signature) {
 		this(-1, signature);
@@ -27,11 +24,8 @@ public class GetArbitraryDataMessage extends Message {
 		return this.signature;
 	}
 
-	public static Message fromByteBuffer(int id, ByteBuffer bytes) throws UnsupportedEncodingException {
-		if (bytes.remaining() != SIGNATURE_LENGTH)
-			return null;
-
-		byte[] signature = new byte[SIGNATURE_LENGTH];
+	public static Message fromByteBuffer(int id, ByteBuffer bytes) {
+		byte[] signature = new byte[Transformer.SIGNATURE_LENGTH];
 
 		bytes.get(signature);
 
@@ -39,16 +33,12 @@ public class GetArbitraryDataMessage extends Message {
 	}
 
 	@Override
-	protected byte[] toData() {
-		try {
-			ByteArrayOutputStream bytes = new ByteArrayOutputStream();
+	protected byte[] toData() throws IOException {
+		ByteArrayOutputStream bytes = new ByteArrayOutputStream();
 
-			bytes.write(this.signature);
+		bytes.write(this.signature);
 
-			return bytes.toByteArray();
-		} catch (IOException e) {
-			return null;
-		}
+		return bytes.toByteArray();
 	}
 
 }

src/main/java/org/qortal/network/message/GetArbitraryMetadataMessage.java

@@ -6,16 +6,10 @@ import org.qortal.transform.Transformer;
 
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
-import java.io.UnsupportedEncodingException;
 import java.nio.ByteBuffer;
 
-import static org.qortal.transform.Transformer.INT_LENGTH;
-import static org.qortal.transform.Transformer.LONG_LENGTH;
-
 public class GetArbitraryMetadataMessage extends Message {
 
-	private static final int SIGNATURE_LENGTH = Transformer.SIGNATURE_LENGTH;
-
 	private final byte[] signature;
 	private final long requestTime;
 	private int requestHops;
@@ -36,12 +30,8 @@ public class GetArbitraryMetadataMessage extends Message {
 		return this.signature;
 	}
 
-	public static Message fromByteBuffer(int id, ByteBuffer bytes) throws UnsupportedEncodingException {
-		if (bytes.remaining() != SIGNATURE_LENGTH + LONG_LENGTH + INT_LENGTH)
-			return null;
-
-		byte[] signature = new byte[SIGNATURE_LENGTH];
-
+	public static Message fromByteBuffer(int id, ByteBuffer bytes) {
+		byte[] signature = new byte[Transformer.SIGNATURE_LENGTH];
 		bytes.get(signature);
 
 		long requestTime = bytes.getLong();
@@ -52,20 +42,16 @@ public class GetArbitraryMetadataMessage extends Message {
 	}
 
 	@Override
-	protected byte[] toData() {
-		try {
-			ByteArrayOutputStream bytes = new ByteArrayOutputStream();
+	protected byte[] toData() throws IOException {
+		ByteArrayOutputStream bytes = new ByteArrayOutputStream();
 
-			bytes.write(this.signature);
+		bytes.write(this.signature);
 
-			bytes.write(Longs.toByteArray(this.requestTime));
+		bytes.write(Longs.toByteArray(this.requestTime));
 
-			bytes.write(Ints.toByteArray(this.requestHops));
+		bytes.write(Ints.toByteArray(this.requestHops));
 
-			return bytes.toByteArray();
-		} catch (IOException e) {
-			return null;
-		}
+		return bytes.toByteArray();
 	}
 
 	public long getRequestTime() {

src/main/java/org/qortal/network/message/GetBlockMessage.java

@@ -2,16 +2,13 @@ package org.qortal.network.message;
 
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
-import java.io.UnsupportedEncodingException;
 import java.nio.ByteBuffer;
 
 import org.qortal.transform.block.BlockTransformer;
 
 public class GetBlockMessage extends Message {
 
-	private static final int BLOCK_SIGNATURE_LENGTH = BlockTransformer.BLOCK_SIGNATURE_LENGTH;
-
-	private byte[] signature;
+	private final byte[] signature;
 
 	public GetBlockMessage(byte[] signature) {
 		this(-1, signature);
@@ -27,28 +24,20 @@ public class GetBlockMessage extends Message {
 		return this.signature;
 	}
 
-	public static Message fromByteBuffer(int id, ByteBuffer bytes) throws UnsupportedEncodingException {
-		if (bytes.remaining() != BLOCK_SIGNATURE_LENGTH)
-			return null;
-
-		byte[] signature = new byte[BLOCK_SIGNATURE_LENGTH];
-
+	public static Message fromByteBuffer(int id, ByteBuffer bytes) {
+		byte[] signature = new byte[BlockTransformer.BLOCK_SIGNATURE_LENGTH];
 		bytes.get(signature);
 
 		return new GetBlockMessage(id, signature);
 	}
 
 	@Override
-	protected byte[] toData() {
-		try {
-			ByteArrayOutputStream bytes = new ByteArrayOutputStream();
+	protected byte[] toData() throws IOException {
+		ByteArrayOutputStream bytes = new ByteArrayOutputStream();
 
-			bytes.write(this.signature);
+		bytes.write(this.signature);
 
-			return bytes.toByteArray();
-		} catch (IOException e) {
-			return null;
-		}
+		return bytes.toByteArray();
 	}
 
 }

src/main/java/org/qortal/network/message/GetBlockSummariesMessage.java

@@ -2,20 +2,16 @@ package org.qortal.network.message;
 
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
-import java.io.UnsupportedEncodingException;
 import java.nio.ByteBuffer;
 
-import org.qortal.transform.Transformer;
 import org.qortal.transform.block.BlockTransformer;
 
 import com.google.common.primitives.Ints;
 
 public class GetBlockSummariesMessage extends Message {
 
-	private static final int BLOCK_SIGNATURE_LENGTH = BlockTransformer.BLOCK_SIGNATURE_LENGTH;
-
-	private byte[] parentSignature;
-	private int numberRequested;
+	private final byte[] parentSignature;
+	private final int numberRequested;
 
 	public GetBlockSummariesMessage(byte[] parentSignature, int numberRequested) {
 		this(-1, parentSignature, numberRequested);
@@ -36,11 +32,8 @@ public class GetBlockSummariesMessage extends Message {
 		return this.numberRequested;
 	}
 
-	public static Message fromByteBuffer(int id, ByteBuffer bytes) throws UnsupportedEncodingException {
-		if (bytes.remaining() != BLOCK_SIGNATURE_LENGTH + Transformer.INT_LENGTH)
-			return null;
-
-		byte[] parentSignature = new byte[BLOCK_SIGNATURE_LENGTH];
+	public static Message fromByteBuffer(int id, ByteBuffer bytes) {
+		byte[] parentSignature = new byte[BlockTransformer.BLOCK_SIGNATURE_LENGTH];
 		bytes.get(parentSignature);
 
 		int numberRequested = bytes.getInt();
@@ -49,18 +42,14 @@ public class GetBlockSummariesMessage extends Message {
 	}
 
 	@Override
-	protected byte[] toData() {
-		try {
-			ByteArrayOutputStream bytes = new ByteArrayOutputStream();
+	protected byte[] toData() throws IOException {
+		ByteArrayOutputStream bytes = new ByteArrayOutputStream();
 
-			bytes.write(this.parentSignature);
+		bytes.write(this.parentSignature);
 
-			bytes.write(Ints.toByteArray(this.numberRequested));
+		bytes.write(Ints.toByteArray(this.numberRequested));
 
-			return bytes.toByteArray();
-		} catch (IOException e) {
-			return null;
-		}
+		return bytes.toByteArray();
 	}
 
 }

src/main/java/org/qortal/network/message/GetOnlineAccountsMessage.java

@@ -2,7 +2,6 @@ package org.qortal.network.message;
 
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
-import java.io.UnsupportedEncodingException;
 import java.nio.ByteBuffer;
 import java.util.ArrayList;
 import java.util.List;
@@ -17,7 +16,7 @@ import com.google.common.primitives.Longs;
 public class GetOnlineAccountsMessage extends Message {
 	private static final int MAX_ACCOUNT_COUNT = 5000;
 
-	private List<OnlineAccountData> onlineAccounts;
+	private final List<OnlineAccountData> onlineAccounts;
 
 	public GetOnlineAccountsMessage(List<OnlineAccountData> onlineAccounts) {
 		this(-1, onlineAccounts);
@@ -33,7 +32,7 @@ public class GetOnlineAccountsMessage extends Message {
 		return this.onlineAccounts;
 	}
 
-	public static Message fromByteBuffer(int id, ByteBuffer bytes) throws UnsupportedEncodingException {
+	public static Message fromByteBuffer(int id, ByteBuffer bytes) {
 		final int accountCount = bytes.getInt();
 
 		List<OnlineAccountData> onlineAccounts = new ArrayList<>(accountCount);
@@ -51,23 +50,18 @@ public class GetOnlineAccountsMessage extends Message {
 	}
 
 	@Override
-	protected byte[] toData() {
-		try {
-			ByteArrayOutputStream bytes = new ByteArrayOutputStream();
+	protected byte[] toData() throws IOException {
+		ByteArrayOutputStream bytes = new ByteArrayOutputStream();
 
-			bytes.write(Ints.toByteArray(this.onlineAccounts.size()));
+		bytes.write(Ints.toByteArray(this.onlineAccounts.size()));
 
-			for (int i = 0; i < this.onlineAccounts.size(); ++i) {
-				OnlineAccountData onlineAccountData = this.onlineAccounts.get(i);
-				bytes.write(Longs.toByteArray(onlineAccountData.getTimestamp()));
+		for (OnlineAccountData onlineAccountData : this.onlineAccounts) {
+			bytes.write(Longs.toByteArray(onlineAccountData.getTimestamp()));
 
-				bytes.write(onlineAccountData.getPublicKey());
-			}
-
-			return bytes.toByteArray();
-		} catch (IOException e) {
-			return null;
+			bytes.write(onlineAccountData.getPublicKey());
 		}
+
+		return bytes.toByteArray();
 	}
 
 }

src/main/java/org/qortal/network/message/GetOnlineAccountsV2Message.java

@@ -7,7 +7,6 @@ import org.qortal.transform.Transformer;
 
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
-import java.io.UnsupportedEncodingException;
 import java.nio.ByteBuffer;
 import java.util.ArrayList;
 import java.util.HashMap;
@@ -24,7 +23,7 @@ import java.util.Map;
  * Also V2 only builds online accounts message once!
  */
 public class GetOnlineAccountsV2Message extends Message {
-	private List<OnlineAccountData> onlineAccounts;
+	private final List<OnlineAccountData> onlineAccounts;
 	private byte[] cachedData;
 
 	public GetOnlineAccountsV2Message(List<OnlineAccountData> onlineAccounts) {
@@ -41,7 +40,7 @@ public class GetOnlineAccountsV2Message extends Message {
 		return this.onlineAccounts;
 	}
 
-	public static Message fromByteBuffer(int id, ByteBuffer bytes) throws UnsupportedEncodingException {
+	public static Message fromByteBuffer(int id, ByteBuffer bytes) {
 		int accountCount = bytes.getInt();
 
 		List<OnlineAccountData> onlineAccounts = new ArrayList<>(accountCount);
@@ -68,7 +67,7 @@ public class GetOnlineAccountsV2Message extends Message {
 	}
 
 	@Override
-	protected synchronized byte[] toData() {
+	protected synchronized byte[] toData() throws IOException {
 		if (this.cachedData != null)
 			return this.cachedData;
 
@@ -81,8 +80,7 @@ public class GetOnlineAccountsV2Message extends Message {
 		// How many of each timestamp
 		Map<Long, Integer> countByTimestamp = new HashMap<>();
 
-		for (int i = 0; i < this.onlineAccounts.size(); ++i) {
-			OnlineAccountData onlineAccountData = this.onlineAccounts.get(i);
+		for (OnlineAccountData onlineAccountData : this.onlineAccounts) {
 			Long timestamp = onlineAccountData.getTimestamp();
 			countByTimestamp.compute(timestamp, (k, v) -> v == null ? 1 : ++v);
 		}
@@ -91,27 +89,21 @@ public class GetOnlineAccountsV2Message extends Message {
 		int byteSize = countByTimestamp.size() * (Transformer.INT_LENGTH + Transformer.TIMESTAMP_LENGTH)
 				+ this.onlineAccounts.size() * Transformer.PUBLIC_KEY_LENGTH;
 
-		try {
-			ByteArrayOutputStream bytes = new ByteArrayOutputStream(byteSize);
+		ByteArrayOutputStream bytes = new ByteArrayOutputStream(byteSize);
 
-			for (long timestamp : countByTimestamp.keySet()) {
-				bytes.write(Ints.toByteArray(countByTimestamp.get(timestamp)));
+		for (long timestamp : countByTimestamp.keySet()) {
+			bytes.write(Ints.toByteArray(countByTimestamp.get(timestamp)));
 
-				bytes.write(Longs.toByteArray(timestamp));
+			bytes.write(Longs.toByteArray(timestamp));
 
-				for (int i = 0; i < this.onlineAccounts.size(); ++i) {
-					OnlineAccountData onlineAccountData = this.onlineAccounts.get(i);
-
-					if (onlineAccountData.getTimestamp() == timestamp)
-						bytes.write(onlineAccountData.getPublicKey());
-				}
+			for (OnlineAccountData onlineAccountData : this.onlineAccounts) {
+				if (onlineAccountData.getTimestamp() == timestamp)
+					bytes.write(onlineAccountData.getPublicKey());
 			}
-
-			this.cachedData = bytes.toByteArray();
-			return this.cachedData;
-		} catch (IOException e) {
-			return null;
 		}
+
+		this.cachedData = bytes.toByteArray();
+		return this.cachedData;
 	}
 
 }

src/main/java/org/qortal/network/message/GetPeersMessage.java

@@ -1,6 +1,5 @@
 package org.qortal.network.message;
 
-import java.io.UnsupportedEncodingException;
 import java.nio.ByteBuffer;
 
 public class GetPeersMessage extends Message {
@@ -13,7 +12,7 @@ public class GetPeersMessage extends Message {
 		super(id, MessageType.GET_PEERS);
 	}
 
-	public static Message fromByteBuffer(int id, ByteBuffer bytes) throws UnsupportedEncodingException {
+	public static Message fromByteBuffer(int id, ByteBuffer bytes) {
 		return new GetPeersMessage(id);
 	}
 

src/main/java/org/qortal/network/message/GetSignaturesV2Message.java

@@ -2,21 +2,16 @@ package org.qortal.network.message;
 
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
-import java.io.UnsupportedEncodingException;
 import java.nio.ByteBuffer;
 
-import org.qortal.transform.Transformer;
 import org.qortal.transform.block.BlockTransformer;
 
 import com.google.common.primitives.Ints;
 
 public class GetSignaturesV2Message extends Message {
 
-	private static final int BLOCK_SIGNATURE_LENGTH = BlockTransformer.BLOCK_SIGNATURE_LENGTH;
-	private static final int NUMBER_REQUESTED_LENGTH = Transformer.INT_LENGTH;
-
-	private byte[] parentSignature;
-	private int numberRequested;
+	private final byte[] parentSignature;
+	private final int numberRequested;
 
 	public GetSignaturesV2Message(byte[] parentSignature, int numberRequested) {
 		this(-1, parentSignature, numberRequested);
@@ -37,11 +32,8 @@ public class GetSignaturesV2Message extends Message {
 		return this.numberRequested;
 	}
 
-	public static Message fromByteBuffer(int id, ByteBuffer bytes) throws UnsupportedEncodingException {
-		if (bytes.remaining() != BLOCK_SIGNATURE_LENGTH + NUMBER_REQUESTED_LENGTH)
-			return null;
-
-		byte[] parentSignature = new byte[BLOCK_SIGNATURE_LENGTH];
+	public static Message fromByteBuffer(int id, ByteBuffer bytes) {
+		byte[] parentSignature = new byte[BlockTransformer.BLOCK_SIGNATURE_LENGTH];
 		bytes.get(parentSignature);
 
 		int numberRequested = bytes.getInt();
@@ -50,18 +42,14 @@ public class GetSignaturesV2Message extends Message {
 	}
 
 	@Override
-	protected byte[] toData() {
-		try {
-			ByteArrayOutputStream bytes = new ByteArrayOutputStream();
+	protected byte[] toData() throws IOException {
+		ByteArrayOutputStream bytes = new ByteArrayOutputStream();
 
-			bytes.write(this.parentSignature);
+		bytes.write(this.parentSignature);
 
-			bytes.write(Ints.toByteArray(this.numberRequested));
+		bytes.write(Ints.toByteArray(this.numberRequested));
 
-			return bytes.toByteArray();
-		} catch (IOException e) {
-			return null;
-		}
+		return bytes.toByteArray();
 	}
 
 }

src/main/java/org/qortal/network/message/GetTradePresencesMessage.java

@@ -7,7 +7,6 @@ import org.qortal.transform.Transformer;
 
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
-import java.io.UnsupportedEncodingException;
 import java.nio.ByteBuffer;
 import java.util.ArrayList;
 import java.util.HashMap;
@@ -20,7 +19,7 @@ import java.util.Map;
  * Groups of: number of entries, timestamp, then AT trade pubkey for each entry.
  */
 public class GetTradePresencesMessage extends Message {
-	private List<TradePresenceData> tradePresences;
+	private final List<TradePresenceData> tradePresences;
 	private byte[] cachedData;
 
 	public GetTradePresencesMessage(List<TradePresenceData> tradePresences) {
@@ -37,7 +36,7 @@ public class GetTradePresencesMessage extends Message {
 		return this.tradePresences;
 	}
 
-	public static Message fromByteBuffer(int id, ByteBuffer bytes) throws UnsupportedEncodingException {
+	public static Message fromByteBuffer(int id, ByteBuffer bytes) {
 		int groupedEntriesCount = bytes.getInt();
 
 		List<TradePresenceData> tradePresences = new ArrayList<>(groupedEntriesCount);
@@ -64,7 +63,7 @@ public class GetTradePresencesMessage extends Message {
 	}
 
 	@Override
-	protected synchronized byte[] toData() {
+	protected synchronized byte[] toData() throws IOException {
 		if (this.cachedData != null)
 			return this.cachedData;
 
@@ -86,25 +85,21 @@ public class GetTradePresencesMessage extends Message {
 		int byteSize = countByTimestamp.size() * (Transformer.INT_LENGTH + Transformer.TIMESTAMP_LENGTH)
 				+ this.tradePresences.size() * Transformer.PUBLIC_KEY_LENGTH;
 
-		try {
-			ByteArrayOutputStream bytes = new ByteArrayOutputStream(byteSize);
+		ByteArrayOutputStream bytes = new ByteArrayOutputStream(byteSize);
 
-			for (long timestamp : countByTimestamp.keySet()) {
-				bytes.write(Ints.toByteArray(countByTimestamp.get(timestamp)));
+		for (long timestamp : countByTimestamp.keySet()) {
+			bytes.write(Ints.toByteArray(countByTimestamp.get(timestamp)));
 
-				bytes.write(Longs.toByteArray(timestamp));
+			bytes.write(Longs.toByteArray(timestamp));
 
-				for (TradePresenceData tradePresenceData : this.tradePresences) {
-					if (tradePresenceData.getTimestamp() == timestamp)
-						bytes.write(tradePresenceData.getPublicKey());
-				}
+			for (TradePresenceData tradePresenceData : this.tradePresences) {
+				if (tradePresenceData.getTimestamp() == timestamp)
+					bytes.write(tradePresenceData.getPublicKey());
 			}
-
-			this.cachedData = bytes.toByteArray();
-			return this.cachedData;
-		} catch (IOException e) {
-			return null;
 		}
+
+		this.cachedData = bytes.toByteArray();
+		return this.cachedData;
 	}
 
 }

src/main/java/org/qortal/network/message/GetTransactionMessage.java

@@ -2,16 +2,13 @@ package org.qortal.network.message;
 
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
-import java.io.UnsupportedEncodingException;
 import java.nio.ByteBuffer;
 
 import org.qortal.transform.Transformer;
 
 public class GetTransactionMessage extends Message {
 
-	private static final int TRANSACTION_SIGNATURE_LENGTH = Transformer.SIGNATURE_LENGTH;
-
-	private byte[] signature;
+	private final byte[] signature;
 
 	public GetTransactionMessage(byte[] signature) {
 		this(-1, signature);
@@ -27,11 +24,8 @@ public class GetTransactionMessage extends Message {
 		return this.signature;
 	}
 
-	public static Message fromByteBuffer(int id, ByteBuffer bytes) throws UnsupportedEncodingException {
-		if (bytes.remaining() != TRANSACTION_SIGNATURE_LENGTH)
-			return null;
-
-		byte[] signature = new byte[TRANSACTION_SIGNATURE_LENGTH];
+	public static Message fromByteBuffer(int id, ByteBuffer bytes) {
+		byte[] signature = new byte[Transformer.SIGNATURE_LENGTH];
 
 		bytes.get(signature);
 
@@ -39,16 +33,12 @@ public class GetTransactionMessage extends Message {
 	}
 
 	@Override
-	protected byte[] toData() {
-		try {
-			ByteArrayOutputStream bytes = new ByteArrayOutputStream();
+	protected byte[] toData() throws IOException {
+		ByteArrayOutputStream bytes = new ByteArrayOutputStream();
 
-			bytes.write(this.signature);
+		bytes.write(this.signature);
 
-			return bytes.toByteArray();
-		} catch (IOException e) {
-			return null;
-		}
+		return bytes.toByteArray();
 	}
 
 }

src/main/java/org/qortal/network/message/GetUnconfirmedTransactionsMessage.java

@@ -1,6 +1,5 @@
 package org.qortal.network.message;
 
-import java.io.UnsupportedEncodingException;
 import java.nio.ByteBuffer;
 
 public class GetUnconfirmedTransactionsMessage extends Message {
@@ -13,7 +12,7 @@ public class GetUnconfirmedTransactionsMessage extends Message {
 		super(id, MessageType.GET_UNCONFIRMED_TRANSACTIONS);
 	}
 
-	public static Message fromByteBuffer(int id, ByteBuffer bytes) throws UnsupportedEncodingException {
+	public static Message fromByteBuffer(int id, ByteBuffer bytes) {
 		return new GetUnconfirmedTransactionsMessage(id);
 	}
 

src/main/java/org/qortal/network/message/GoodbyeMessage.java

@@ -22,7 +22,7 @@ public class GoodbyeMessage extends Message {
 		private static final Map<Integer, Reason> map = stream(Reason.values())
 				.collect(toMap(reason -> reason.value, reason -> reason));
 
-		private Reason(int value) {
+		Reason(int value) {
 			this.value = value;
 		}
 
@@ -47,12 +47,12 @@ public class GoodbyeMessage extends Message {
 		return this.reason;
 	}
 
-	public static Message fromByteBuffer(int id, ByteBuffer byteBuffer) {
+	public static Message fromByteBuffer(int id, ByteBuffer byteBuffer) throws MessageException {
 		int reasonValue = byteBuffer.getInt();
 
 		Reason reason = Reason.valueOf(reasonValue);
 		if (reason == null)
-			return null;
+			throw new MessageException("Invalid reason " + reasonValue + " in GOODBYE message");
 
 		return new GoodbyeMessage(id, reason);
 	}

src/main/java/org/qortal/network/message/HeightV2Message.java

@@ -2,7 +2,6 @@ package org.qortal.network.message;
 
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
-import java.io.UnsupportedEncodingException;
 import java.nio.ByteBuffer;
 
 import org.qortal.transform.Transformer;
@@ -13,10 +12,10 @@ import com.google.common.primitives.Longs;
 
 public class HeightV2Message extends Message {
 
-	private int height;
-	private byte[] signature;
-	private long timestamp;
-	private byte[] minterPublicKey;
+	private final int height;
+	private final byte[] signature;
+	private final long timestamp;
+	private final byte[] minterPublicKey;
 
 	public HeightV2Message(int height, byte[] signature, long timestamp, byte[] minterPublicKey) {
 		this(-1, height, signature, timestamp, minterPublicKey);
@@ -47,7 +46,7 @@ public class HeightV2Message extends Message {
 		return this.minterPublicKey;
 	}
 
-	public static Message fromByteBuffer(int id, ByteBuffer bytes) throws UnsupportedEncodingException {
+	public static Message fromByteBuffer(int id, ByteBuffer bytes) {
 		int height = bytes.getInt();
 
 		byte[] signature = new byte[BlockTransformer.BLOCK_SIGNATURE_LENGTH];
@@ -62,22 +61,18 @@ public class HeightV2Message extends Message {
 	}
 
 	@Override
-	protected byte[] toData() {
-		try {
-			ByteArrayOutputStream bytes = new ByteArrayOutputStream();
+	protected byte[] toData() throws IOException {
+		ByteArrayOutputStream bytes = new ByteArrayOutputStream();
 
-			bytes.write(Ints.toByteArray(this.height));
+		bytes.write(Ints.toByteArray(this.height));
 
-			bytes.write(this.signature);
+		bytes.write(this.signature);
 
-			bytes.write(Longs.toByteArray(this.timestamp));
+		bytes.write(Longs.toByteArray(this.timestamp));
 
-			bytes.write(this.minterPublicKey);
+		bytes.write(this.minterPublicKey);
 
-			return bytes.toByteArray();
-		} catch (IOException e) {
-			return null;
-		}
+		return bytes.toByteArray();
 	}
 
 }

src/main/java/org/qortal/network/message/HelloMessage.java

@@ -39,15 +39,20 @@ public class HelloMessage extends Message {
 		return this.senderPeerAddress;
 	}
 
-	public static Message fromByteBuffer(int id, ByteBuffer byteBuffer) throws TransformationException {
+	public static Message fromByteBuffer(int id, ByteBuffer byteBuffer) throws MessageException {
 		long timestamp = byteBuffer.getLong();
 
-		String versionString = Serialization.deserializeSizedString(byteBuffer, 255);
-
-		// Sender peer address added in v3.0, so is an optional field. Older versions won't send it.
+		String versionString;
 		String senderPeerAddress = null;
-		if (byteBuffer.hasRemaining()) {
-			senderPeerAddress = Serialization.deserializeSizedString(byteBuffer, 255);
+		try {
+			versionString = Serialization.deserializeSizedString(byteBuffer, 255);
+
+			// Sender peer address added in v3.0, so is an optional field. Older versions won't send it.
+			if (byteBuffer.hasRemaining()) {
+				senderPeerAddress = Serialization.deserializeSizedString(byteBuffer, 255);
+			}
+		} catch (TransformationException e) {
+			throw new MessageException(e.getMessage(), e);
 		}
 
 		return new HelloMessage(id, timestamp, versionString, senderPeerAddress);

src/main/java/org/qortal/network/message/Message.java

@@ -1,7 +1,5 @@
 package org.qortal.network.message;
 
-import java.util.Map;
-
 import org.qortal.crypto.Crypto;
 import org.qortal.network.Network;
 import org.qortal.transform.TransformationException;
@@ -13,8 +11,6 @@ import static java.util.stream.Collectors.toMap;
 
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
-import java.lang.reflect.InvocationTargetException;
-import java.lang.reflect.Method;
 import java.nio.BufferUnderflowException;
 import java.nio.ByteBuffer;
 import java.util.Arrays;
@@ -27,127 +23,6 @@ public abstract class Message {
 
 	private static final int MAX_DATA_SIZE = 10 * 1024 * 1024; // 10MB
 
-	@SuppressWarnings("serial")
-	public static class MessageException extends Exception {
-		public MessageException() {
-		}
-
-		public MessageException(String message) {
-			super(message);
-		}
-
-		public MessageException(String message, Throwable cause) {
-			super(message, cause);
-		}
-
-		public MessageException(Throwable cause) {
-			super(cause);
-		}
-	}
-
-	public enum MessageType {
-		// Handshaking
-		HELLO(0),
-		GOODBYE(1),
-		CHALLENGE(2),
-		RESPONSE(3),
-
-		// Status / notifications
-		HEIGHT_V2(10),
-		PING(11),
-		PONG(12),
-
-		// Requesting data
-		PEERS_V2(20),
-		GET_PEERS(21),
-
-		TRANSACTION(30),
-		GET_TRANSACTION(31),
-
-		TRANSACTION_SIGNATURES(40),
-		GET_UNCONFIRMED_TRANSACTIONS(41),
-
-		BLOCK(50),
-		GET_BLOCK(51),
-
-		SIGNATURES(60),
-		GET_SIGNATURES_V2(61),
-
-		BLOCK_SUMMARIES(70),
-		GET_BLOCK_SUMMARIES(71),
-
-		ONLINE_ACCOUNTS(80),
-		GET_ONLINE_ACCOUNTS(81),
-		ONLINE_ACCOUNTS_V2(82),
-		GET_ONLINE_ACCOUNTS_V2(83),
-
-		ARBITRARY_DATA(90),
-		GET_ARBITRARY_DATA(91),
-
-		BLOCKS(100),
-		GET_BLOCKS(101),
-
-		ARBITRARY_DATA_FILE(110),
-		GET_ARBITRARY_DATA_FILE(111),
-
-		ARBITRARY_DATA_FILE_LIST(120),
-		GET_ARBITRARY_DATA_FILE_LIST(121),
-
-		ARBITRARY_SIGNATURES(130),
-
-		TRADE_PRESENCES(140),
-		GET_TRADE_PRESENCES(141),
-		
-		ARBITRARY_METADATA(150),
-		GET_ARBITRARY_METADATA(151);
-
-		public final int value;
-		public final Method fromByteBufferMethod;
-
-		private static final Map<Integer, MessageType> map = stream(MessageType.values())
-				.collect(toMap(messageType -> messageType.value, messageType -> messageType));
-
-		private MessageType(int value) {
-			this.value = value;
-
-			String[] classNameParts = this.name().toLowerCase().split("_");
-
-			for (int i = 0; i < classNameParts.length; ++i)
-				classNameParts[i] = classNameParts[i].substring(0, 1).toUpperCase().concat(classNameParts[i].substring(1));
-
-			String className = String.join("", classNameParts);
-
-			Method method;
-			try {
-				Class<?> subclass = Class.forName(String.join("", Message.class.getPackage().getName(), ".", className, "Message"));
-
-				method = subclass.getDeclaredMethod("fromByteBuffer", int.class, ByteBuffer.class);
-			} catch (ClassNotFoundException | NoSuchMethodException | SecurityException e) {
-				method = null;
-			}
-
-			this.fromByteBufferMethod = method;
-		}
-
-		public static MessageType valueOf(int value) {
-			return map.get(value);
-		}
-
-		public Message fromByteBuffer(int id, ByteBuffer byteBuffer) throws MessageException {
-			if (this.fromByteBufferMethod == null)
-				throw new MessageException("Unsupported message type [" + value + "] during conversion from bytes");
-
-			try {
-				return (Message) this.fromByteBufferMethod.invoke(null, id, byteBuffer);
-			} catch (IllegalAccessException | IllegalArgumentException | InvocationTargetException e) {
-				if (e.getCause() instanceof BufferUnderflowException)
-					throw new MessageException("Byte data too short for " + name() + " message");
-
-				throw new MessageException("Internal error with " + name() + " message during conversion from bytes");
-			}
-		}
-	}
-
 	private int id;
 	private MessageType type;
 
@@ -181,7 +56,7 @@ public abstract class Message {
 	 * 
 	 * @param readOnlyBuffer
 	 * @return null if no complete message can be read
-	 * @throws MessageException
+	 * @throws MessageException if message could not be decoded or is invalid
 	 */
 	public static Message fromByteBuffer(ByteBuffer readOnlyBuffer) throws MessageException {
 		try {
@@ -293,6 +168,12 @@ public abstract class Message {
 		}
 	}
 
+	/** Serialize message into bytes.
+	 *
+	 * @return message as byte array, or null if message is missing payload data / uninitialized somehow
+	 * @throws IOException if unable / failed to serialize
+	 * @throws TransformationException if unable / failed to serialize
+	 */
 	protected abstract byte[] toData() throws IOException, TransformationException;
 
 }

src/main/java/org/qortal/network/message/MessageException.java

@@ -0,0 +1,19 @@
+package org.qortal.network.message;
+
+@SuppressWarnings("serial")
+public class MessageException extends Exception {
+    public MessageException() {
+    }
+
+    public MessageException(String message) {
+        super(message);
+    }
+
+    public MessageException(String message, Throwable cause) {
+        super(message, cause);
+    }
+
+    public MessageException(Throwable cause) {
+        super(cause);
+    }
+}

src/main/java/org/qortal/network/message/MessageProducer.java

@@ -0,0 +1,8 @@
+package org.qortal.network.message;
+
+import java.nio.ByteBuffer;
+
+@FunctionalInterface
+public interface MessageProducer {
+    Message fromByteBuffer(int id, ByteBuffer byteBuffer) throws MessageException;
+}

src/main/java/org/qortal/network/message/MessageType.java

@@ -0,0 +1,96 @@
+package org.qortal.network.message;
+
+import java.nio.BufferUnderflowException;
+import java.nio.ByteBuffer;
+import java.util.Map;
+
+import static java.util.Arrays.stream;
+import static java.util.stream.Collectors.toMap;
+
+public enum MessageType {
+    // Handshaking
+    HELLO(0, HelloMessage::fromByteBuffer),
+    GOODBYE(1, GoodbyeMessage::fromByteBuffer),
+    CHALLENGE(2, ChallengeMessage::fromByteBuffer),
+    RESPONSE(3, ResponseMessage::fromByteBuffer),
+
+    // Status / notifications
+    HEIGHT_V2(10, HeightV2Message::fromByteBuffer),
+    PING(11, PingMessage::fromByteBuffer),
+    PONG(12, PongMessage::fromByteBuffer),
+
+    // Requesting data
+    PEERS_V2(20, PeersV2Message::fromByteBuffer),
+    GET_PEERS(21, GetPeersMessage::fromByteBuffer),
+
+    TRANSACTION(30, TransactionMessage::fromByteBuffer),
+    GET_TRANSACTION(31, GetTransactionMessage::fromByteBuffer),
+
+    TRANSACTION_SIGNATURES(40, TransactionSignaturesMessage::fromByteBuffer),
+    GET_UNCONFIRMED_TRANSACTIONS(41, GetUnconfirmedTransactionsMessage::fromByteBuffer),
+
+    BLOCK(50, BlockMessage::fromByteBuffer),
+    GET_BLOCK(51, GetBlockMessage::fromByteBuffer),
+
+    SIGNATURES(60, SignaturesMessage::fromByteBuffer),
+    GET_SIGNATURES_V2(61, GetSignaturesV2Message::fromByteBuffer),
+
+    BLOCK_SUMMARIES(70, BlockSummariesMessage::fromByteBuffer),
+    GET_BLOCK_SUMMARIES(71, GetBlockSummariesMessage::fromByteBuffer),
+
+    ONLINE_ACCOUNTS(80, OnlineAccountsMessage::fromByteBuffer),
+    GET_ONLINE_ACCOUNTS(81, GetOnlineAccountsMessage::fromByteBuffer),
+    ONLINE_ACCOUNTS_V2(82, OnlineAccountsV2Message::fromByteBuffer),
+    GET_ONLINE_ACCOUNTS_V2(83, GetOnlineAccountsV2Message::fromByteBuffer),
+
+    ARBITRARY_DATA(90, ArbitraryDataMessage::fromByteBuffer),
+    GET_ARBITRARY_DATA(91, GetArbitraryDataMessage::fromByteBuffer),
+
+    BLOCKS(100, null), // unsupported
+    GET_BLOCKS(101, null), // unsupported
+
+    ARBITRARY_DATA_FILE(110, ArbitraryDataFileMessage::fromByteBuffer),
+    GET_ARBITRARY_DATA_FILE(111, GetArbitraryDataFileMessage::fromByteBuffer),
+
+    ARBITRARY_DATA_FILE_LIST(120, ArbitraryDataFileListMessage::fromByteBuffer),
+    GET_ARBITRARY_DATA_FILE_LIST(121, GetArbitraryDataFileListMessage::fromByteBuffer),
+
+    ARBITRARY_SIGNATURES(130, ArbitrarySignaturesMessage::fromByteBuffer),
+
+    TRADE_PRESENCES(140, TradePresencesMessage::fromByteBuffer),
+    GET_TRADE_PRESENCES(141, GetTradePresencesMessage::fromByteBuffer),
+
+    ARBITRARY_METADATA(150, ArbitraryMetadataMessage::fromByteBuffer),
+    GET_ARBITRARY_METADATA(151, GetArbitraryMetadataMessage::fromByteBuffer);
+
+    public final int value;
+    public final MessageProducer fromByteBufferMethod;
+
+    private static final Map<Integer, MessageType> map = stream(MessageType.values())
+            .collect(toMap(messageType -> messageType.value, messageType -> messageType));
+
+    MessageType(int value, MessageProducer fromByteBufferMethod) {
+        this.value = value;
+        this.fromByteBufferMethod = fromByteBufferMethod;
+    }
+
+    public static MessageType valueOf(int value) {
+        return map.get(value);
+    }
+
+    /**
+     * Attempt to read a message from byte buffer.
+     *
+     * @param id message ID or -1
+     * @param byteBuffer ByteBuffer source for message
+     * @return null if no complete message can be read
+     * @throws MessageException if message could not be decoded or is invalid
+     * @throws BufferUnderflowException if not enough bytes in buffer to read message
+     */
+    public Message fromByteBuffer(int id, ByteBuffer byteBuffer) throws MessageException {
+        if (this.fromByteBufferMethod == null)
+            throw new MessageException("Message type " + this.name() + " unsupported");
+
+        return this.fromByteBufferMethod.fromByteBuffer(id, byteBuffer);
+    }
+}

src/main/java/org/qortal/network/message/OnlineAccountsMessage.java

@@ -2,7 +2,6 @@ package org.qortal.network.message;
 
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
-import java.io.UnsupportedEncodingException;
 import java.nio.ByteBuffer;
 import java.util.ArrayList;
 import java.util.List;
@@ -17,7 +16,7 @@ import com.google.common.primitives.Longs;
 public class OnlineAccountsMessage extends Message {
 	private static final int MAX_ACCOUNT_COUNT = 5000;
 
-	private List<OnlineAccountData> onlineAccounts;
+	private final List<OnlineAccountData> onlineAccounts;
 
 	public OnlineAccountsMessage(List<OnlineAccountData> onlineAccounts) {
 		this(-1, onlineAccounts);
@@ -33,7 +32,7 @@ public class OnlineAccountsMessage extends Message {
 		return this.onlineAccounts;
 	}
 
-	public static Message fromByteBuffer(int id, ByteBuffer bytes) throws UnsupportedEncodingException {
+	public static Message fromByteBuffer(int id, ByteBuffer bytes) {
 		final int accountCount = bytes.getInt();
 
 		List<OnlineAccountData> onlineAccounts = new ArrayList<>(accountCount);
@@ -55,26 +54,20 @@ public class OnlineAccountsMessage extends Message {
 	}
 
 	@Override
-	protected byte[] toData() {
-		try {
-			ByteArrayOutputStream bytes = new ByteArrayOutputStream();
+	protected byte[] toData() throws IOException {
+		ByteArrayOutputStream bytes = new ByteArrayOutputStream();
 
-			bytes.write(Ints.toByteArray(this.onlineAccounts.size()));
+		bytes.write(Ints.toByteArray(this.onlineAccounts.size()));
 
-			for (int i = 0; i < this.onlineAccounts.size(); ++i) {
-				OnlineAccountData onlineAccountData = this.onlineAccounts.get(i);
+		for (OnlineAccountData onlineAccountData : this.onlineAccounts) {
+			bytes.write(Longs.toByteArray(onlineAccountData.getTimestamp()));
 
-				bytes.write(Longs.toByteArray(onlineAccountData.getTimestamp()));
+			bytes.write(onlineAccountData.getSignature());
 
-				bytes.write(onlineAccountData.getSignature());
-
-				bytes.write(onlineAccountData.getPublicKey());
-			}
-
-			return bytes.toByteArray();
-		} catch (IOException e) {
-			return null;
+			bytes.write(onlineAccountData.getPublicKey());
 		}
+
+		return bytes.toByteArray();
 	}
 
 }

src/main/java/org/qortal/network/message/OnlineAccountsV2Message.java

@@ -7,13 +7,11 @@ import org.qortal.transform.Transformer;
 
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
-import java.io.UnsupportedEncodingException;
 import java.nio.ByteBuffer;
 import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
-import java.util.stream.Collectors;
 
 /**
  * For sending online accounts info to remote peer.
@@ -25,7 +23,7 @@ import java.util.stream.Collectors;
  * Also V2 only builds online accounts message once!
  */
 public class OnlineAccountsV2Message extends Message {
-	private List<OnlineAccountData> onlineAccounts;
+	private final List<OnlineAccountData> onlineAccounts;
 	private byte[] cachedData;
 
 	public OnlineAccountsV2Message(List<OnlineAccountData> onlineAccounts) {
@@ -42,7 +40,7 @@ public class OnlineAccountsV2Message extends Message {
 		return this.onlineAccounts;
 	}
 
-	public static Message fromByteBuffer(int id, ByteBuffer bytes) throws UnsupportedEncodingException {
+	public static Message fromByteBuffer(int id, ByteBuffer bytes) throws MessageException {
 		int accountCount = bytes.getInt();
 
 		List<OnlineAccountData> onlineAccounts = new ArrayList<>(accountCount);
@@ -72,7 +70,7 @@ public class OnlineAccountsV2Message extends Message {
 	}
 
 	@Override
-	protected synchronized byte[] toData() {
+	protected synchronized byte[] toData() throws IOException {
 		if (this.cachedData != null)
 			return this.cachedData;
 
@@ -85,8 +83,7 @@ public class OnlineAccountsV2Message extends Message {
 		// How many of each timestamp
 		Map<Long, Integer> countByTimestamp = new HashMap<>();
 
-		for (int i = 0; i < this.onlineAccounts.size(); ++i) {
-			OnlineAccountData onlineAccountData = this.onlineAccounts.get(i);
+		for (OnlineAccountData onlineAccountData : this.onlineAccounts) {
 			Long timestamp = onlineAccountData.getTimestamp();
 			countByTimestamp.compute(timestamp, (k, v) -> v == null ? 1 : ++v);
 		}
@@ -95,30 +92,23 @@ public class OnlineAccountsV2Message extends Message {
 		int byteSize = countByTimestamp.size() * (Transformer.INT_LENGTH + Transformer.TIMESTAMP_LENGTH)
 				+ this.onlineAccounts.size() * (Transformer.SIGNATURE_LENGTH + Transformer.PUBLIC_KEY_LENGTH);
 
-		try {
-			ByteArrayOutputStream bytes = new ByteArrayOutputStream(byteSize);
+		ByteArrayOutputStream bytes = new ByteArrayOutputStream(byteSize);
 
-			for (long timestamp : countByTimestamp.keySet()) {
-				bytes.write(Ints.toByteArray(countByTimestamp.get(timestamp)));
+		for (long timestamp : countByTimestamp.keySet()) {
+			bytes.write(Ints.toByteArray(countByTimestamp.get(timestamp)));
 
-				bytes.write(Longs.toByteArray(timestamp));
+			bytes.write(Longs.toByteArray(timestamp));
 
-				for (int i = 0; i < this.onlineAccounts.size(); ++i) {
-					OnlineAccountData onlineAccountData = this.onlineAccounts.get(i);
-
-					if (onlineAccountData.getTimestamp() == timestamp) {
-						bytes.write(onlineAccountData.getSignature());
-
-						bytes.write(onlineAccountData.getPublicKey());
-					}
+			for (OnlineAccountData onlineAccountData : this.onlineAccounts) {
+				if (onlineAccountData.getTimestamp() == timestamp) {
+					bytes.write(onlineAccountData.getSignature());
+					bytes.write(onlineAccountData.getPublicKey());
 				}
 			}
-
-			this.cachedData = bytes.toByteArray();
-			return this.cachedData;
-		} catch (IOException e) {
-			return null;
 		}
+
+		this.cachedData = bytes.toByteArray();
+		return this.cachedData;
 	}
 
 }

src/main/java/org/qortal/network/message/PeersV2Message.java

@@ -2,7 +2,6 @@ package org.qortal.network.message;
 
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
-import java.io.UnsupportedEncodingException;
 import java.nio.ByteBuffer;
 import java.nio.charset.StandardCharsets;
 import java.util.ArrayList;
@@ -16,7 +15,7 @@ import com.google.common.primitives.Ints;
 // NOTE: this message supports hostnames, literal IP addresses (IPv4 and IPv6) with port numbers
 public class PeersV2Message extends Message {
 
-	private List<PeerAddress> peerAddresses;
+	private final List<PeerAddress> peerAddresses;
 
 	public PeersV2Message(List<PeerAddress> peerAddresses) {
 		this(-1, peerAddresses);
@@ -32,7 +31,7 @@ public class PeersV2Message extends Message {
 		return this.peerAddresses;
 	}
 
-	public static Message fromByteBuffer(int id, ByteBuffer byteBuffer) throws UnsupportedEncodingException {
+	public static Message fromByteBuffer(int id, ByteBuffer byteBuffer) throws MessageException {
 		// Read entry count
 		int count = byteBuffer.getInt();
 
@@ -49,7 +48,7 @@ public class PeersV2Message extends Message {
 				PeerAddress peerAddress = PeerAddress.fromString(addressString);
 				peerAddresses.add(peerAddress);
 			} catch (IllegalArgumentException e) {
-				// Not valid - ignore
+				throw new MessageException("Invalid peer address in received PEERS_V2 message");
 			}
 		}
 
@@ -57,35 +56,31 @@ public class PeersV2Message extends Message {
 	}
 
 	@Override
-	protected byte[] toData() {
-		try {
-			ByteArrayOutputStream bytes = new ByteArrayOutputStream();
+	protected byte[] toData() throws IOException {
+		ByteArrayOutputStream bytes = new ByteArrayOutputStream();
 
-			List<byte[]> addresses = new ArrayList<>();
+		List<byte[]> addresses = new ArrayList<>();
 
-			// First entry represents sending node but contains only port number with empty address.
-			addresses.add(("0.0.0.0:" + Settings.getInstance().getListenPort()).getBytes(StandardCharsets.UTF_8));
+		// First entry represents sending node but contains only port number with empty address.
+		addresses.add(("0.0.0.0:" + Settings.getInstance().getListenPort()).getBytes(StandardCharsets.UTF_8));
 
-			for (PeerAddress peerAddress : this.peerAddresses)
-				addresses.add(peerAddress.toString().getBytes(StandardCharsets.UTF_8));
+		for (PeerAddress peerAddress : this.peerAddresses)
+			addresses.add(peerAddress.toString().getBytes(StandardCharsets.UTF_8));
 
-			// We can't send addresses that are longer than 255 bytes as length itself is encoded in one byte.
-			addresses.removeIf(addressString -> addressString.length > 255);
+		// We can't send addresses that are longer than 255 bytes as length itself is encoded in one byte.
+		addresses.removeIf(addressString -> addressString.length > 255);
 
-			// Serialize
+		// Serialize
 
-			// Number of entries
-			bytes.write(Ints.toByteArray(addresses.size()));
+		// Number of entries
+		bytes.write(Ints.toByteArray(addresses.size()));
 
-			for (byte[] address : addresses) {
-				bytes.write(address.length);
-				bytes.write(address);
-			}
-
-			return bytes.toByteArray();
-		} catch (IOException e) {
-			return null;
+		for (byte[] address : addresses) {
+			bytes.write(address.length);
+			bytes.write(address);
 		}
+
+		return bytes.toByteArray();
 	}
 
 }

src/main/java/org/qortal/network/message/PingMessage.java

@@ -1,6 +1,5 @@
 package org.qortal.network.message;
 
-import java.io.UnsupportedEncodingException;
 import java.nio.ByteBuffer;
 
 public class PingMessage extends Message {
@@ -13,7 +12,7 @@ public class PingMessage extends Message {
 		super(id, MessageType.PING);
 	}
 
-	public static Message fromByteBuffer(int id, ByteBuffer bytes) throws UnsupportedEncodingException {
+	public static Message fromByteBuffer(int id, ByteBuffer bytes) {
 		return new PingMessage(id);
 	}
 

src/main/java/org/qortal/network/message/PongMessage.java

@@ -0,0 +1,24 @@
+package org.qortal.network.message;
+
+import java.nio.ByteBuffer;
+
+public class PongMessage extends Message {
+
+	public PongMessage() {
+		this(-1);
+	}
+
+	private PongMessage(int id) {
+		super(id, MessageType.PONG);
+	}
+
+	public static Message fromByteBuffer(int id, ByteBuffer bytes) {
+		return new PongMessage(id);
+	}
+
+	@Override
+	protected byte[] toData() {
+		return new byte[0];
+	}
+
+}

src/main/java/org/qortal/network/message/SignaturesMessage.java

@@ -2,7 +2,7 @@ package org.qortal.network.message;
 
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
-import java.io.UnsupportedEncodingException;
+import java.nio.BufferUnderflowException;
 import java.nio.ByteBuffer;
 import java.util.ArrayList;
 import java.util.List;
@@ -13,9 +13,7 @@ import com.google.common.primitives.Ints;
 
 public class SignaturesMessage extends Message {
 
-	private static final int BLOCK_SIGNATURE_LENGTH = BlockTransformer.BLOCK_SIGNATURE_LENGTH;
-
-	private List<byte[]> signatures;
+	private final List<byte[]> signatures;
 
 	public SignaturesMessage(List<byte[]> signatures) {
 		this(-1, signatures);
@@ -31,15 +29,15 @@ public class SignaturesMessage extends Message {
 		return this.signatures;
 	}
 
-	public static Message fromByteBuffer(int id, ByteBuffer bytes) throws UnsupportedEncodingException {
+	public static Message fromByteBuffer(int id, ByteBuffer bytes) {
 		int count = bytes.getInt();
 
-		if (bytes.remaining() != count * BLOCK_SIGNATURE_LENGTH)
-			return null;
+		if (bytes.remaining() < count * BlockTransformer.BLOCK_SIGNATURE_LENGTH)
+			throw new BufferUnderflowException();
 
 		List<byte[]> signatures = new ArrayList<>();
 		for (int i = 0; i < count; ++i) {
-			byte[] signature = new byte[BLOCK_SIGNATURE_LENGTH];
+			byte[] signature = new byte[BlockTransformer.BLOCK_SIGNATURE_LENGTH];
 			bytes.get(signature);
 			signatures.add(signature);
 		}
@@ -48,19 +46,15 @@ public class SignaturesMessage extends Message {
 	}
 
 	@Override
-	protected byte[] toData() {
-		try {
-			ByteArrayOutputStream bytes = new ByteArrayOutputStream();
+	protected byte[] toData() throws IOException {
+		ByteArrayOutputStream bytes = new ByteArrayOutputStream();
 
-			bytes.write(Ints.toByteArray(this.signatures.size()));
+		bytes.write(Ints.toByteArray(this.signatures.size()));
 
-			for (byte[] signature : this.signatures)
-				bytes.write(signature);
+		for (byte[] signature : this.signatures)
+			bytes.write(signature);
 
-			return bytes.toByteArray();
-		} catch (IOException e) {
-			return null;
-		}
+		return bytes.toByteArray();
 	}
 
 }

src/main/java/org/qortal/network/message/TradePresencesMessage.java

@@ -8,7 +8,6 @@ import org.qortal.utils.Base58;
 
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
-import java.io.UnsupportedEncodingException;
 import java.nio.ByteBuffer;
 import java.util.ArrayList;
 import java.util.HashMap;
@@ -21,7 +20,7 @@ import java.util.Map;
  * Groups of: number of entries, timestamp, then pubkey + sig + AT address for each entry.
  */
 public class TradePresencesMessage extends Message {
-	private List<TradePresenceData> tradePresences;
+	private final List<TradePresenceData> tradePresences;
 	private byte[] cachedData;
 
 	public TradePresencesMessage(List<TradePresenceData> tradePresences) {
@@ -38,7 +37,7 @@ public class TradePresencesMessage extends Message {
 		return this.tradePresences;
 	}
 
-	public static Message fromByteBuffer(int id, ByteBuffer bytes) throws UnsupportedEncodingException {
+	public static Message fromByteBuffer(int id, ByteBuffer bytes) {
 		int groupedEntriesCount = bytes.getInt();
 
 		List<TradePresenceData> tradePresences = new ArrayList<>(groupedEntriesCount);
@@ -72,7 +71,7 @@ public class TradePresencesMessage extends Message {
 	}
 
 	@Override
-	protected synchronized byte[] toData() {
+	protected synchronized byte[] toData() throws IOException {
 		if (this.cachedData != null)
 			return this.cachedData;
 
@@ -94,30 +93,26 @@ public class TradePresencesMessage extends Message {
 		int byteSize = countByTimestamp.size() * (Transformer.INT_LENGTH + Transformer.TIMESTAMP_LENGTH)
 				+ this.tradePresences.size() * (Transformer.PUBLIC_KEY_LENGTH + Transformer.SIGNATURE_LENGTH + Transformer.ADDRESS_LENGTH);
 
-		try {
-			ByteArrayOutputStream bytes = new ByteArrayOutputStream(byteSize);
+		ByteArrayOutputStream bytes = new ByteArrayOutputStream(byteSize);
 
-			for (long timestamp : countByTimestamp.keySet()) {
-				bytes.write(Ints.toByteArray(countByTimestamp.get(timestamp)));
+		for (long timestamp : countByTimestamp.keySet()) {
+			bytes.write(Ints.toByteArray(countByTimestamp.get(timestamp)));
 
-				bytes.write(Longs.toByteArray(timestamp));
+			bytes.write(Longs.toByteArray(timestamp));
 
-				for (TradePresenceData tradePresenceData : this.tradePresences) {
-					if (tradePresenceData.getTimestamp() == timestamp) {
-						bytes.write(tradePresenceData.getPublicKey());
+			for (TradePresenceData tradePresenceData : this.tradePresences) {
+				if (tradePresenceData.getTimestamp() == timestamp) {
+					bytes.write(tradePresenceData.getPublicKey());
 
-						bytes.write(tradePresenceData.getSignature());
+					bytes.write(tradePresenceData.getSignature());
 
-						bytes.write(Base58.decode(tradePresenceData.getAtAddress()));
-					}
+					bytes.write(Base58.decode(tradePresenceData.getAtAddress()));
 				}
 			}
-
-			this.cachedData = bytes.toByteArray();
-			return this.cachedData;
-		} catch (IOException e) {
-			return null;
 		}
+
+		this.cachedData = bytes.toByteArray();
+		return this.cachedData;
 	}
 
 }

src/main/java/org/qortal/network/message/TransactionMessage.java

@@ -1,6 +1,5 @@
 package org.qortal.network.message;
 
-import java.io.UnsupportedEncodingException;
 import java.nio.ByteBuffer;
 
 import org.qortal.data.transaction.TransactionData;
@@ -25,26 +24,24 @@ public class TransactionMessage extends Message {
 		return this.transactionData;
 	}
 
-	public static Message fromByteBuffer(int id, ByteBuffer byteBuffer) throws UnsupportedEncodingException {
-		try {
-			TransactionData transactionData = TransactionTransformer.fromByteBuffer(byteBuffer);
+	public static Message fromByteBuffer(int id, ByteBuffer byteBuffer) throws MessageException {
+		TransactionData transactionData;
 
-			return new TransactionMessage(id, transactionData);
+		try {
+			transactionData = TransactionTransformer.fromByteBuffer(byteBuffer);
 		} catch (TransformationException e) {
-			return null;
+			throw new MessageException(e.getMessage(), e);
 		}
+
+		return new TransactionMessage(id, transactionData);
 	}
 
 	@Override
-	protected byte[] toData() {
+	protected byte[] toData() throws TransformationException {
 		if (this.transactionData == null)
 			return null;
 
-		try {
-			return TransactionTransformer.toBytes(this.transactionData);
-		} catch (TransformationException e) {
-			return null;
-		}
+		return TransactionTransformer.toBytes(this.transactionData);
 	}
 
 }

src/main/java/org/qortal/network/message/TransactionSignaturesMessage.java

@@ -2,7 +2,7 @@ package org.qortal.network.message;
 
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
-import java.io.UnsupportedEncodingException;
+import java.nio.BufferUnderflowException;
 import java.nio.ByteBuffer;
 import java.util.ArrayList;
 import java.util.List;
@@ -13,9 +13,7 @@ import com.google.common.primitives.Ints;
 
 public class TransactionSignaturesMessage extends Message {
 
-	private static final int SIGNATURE_LENGTH = Transformer.SIGNATURE_LENGTH;
-
-	private List<byte[]> signatures;
+	private final List<byte[]> signatures;
 
 	public TransactionSignaturesMessage(List<byte[]> signatures) {
 		this(-1, signatures);
@@ -31,15 +29,15 @@ public class TransactionSignaturesMessage extends Message {
 		return this.signatures;
 	}
 
-	public static Message fromByteBuffer(int id, ByteBuffer bytes) throws UnsupportedEncodingException {
+	public static Message fromByteBuffer(int id, ByteBuffer bytes) {
 		int count = bytes.getInt();
 
-		if (bytes.remaining() != count * SIGNATURE_LENGTH)
-			return null;
+		if (bytes.remaining() < count * Transformer.SIGNATURE_LENGTH)
+			throw new BufferUnderflowException();
 
 		List<byte[]> signatures = new ArrayList<>();
 		for (int i = 0; i < count; ++i) {
-			byte[] signature = new byte[SIGNATURE_LENGTH];
+			byte[] signature = new byte[Transformer.SIGNATURE_LENGTH];
 			bytes.get(signature);
 			signatures.add(signature);
 		}
@@ -48,19 +46,15 @@ public class TransactionSignaturesMessage extends Message {
 	}
 
 	@Override
-	protected byte[] toData() {
-		try {
-			ByteArrayOutputStream bytes = new ByteArrayOutputStream();
+	protected byte[] toData() throws IOException {
+		ByteArrayOutputStream bytes = new ByteArrayOutputStream();
 
-			bytes.write(Ints.toByteArray(this.signatures.size()));
+		bytes.write(Ints.toByteArray(this.signatures.size()));
 
-			for (byte[] signature : this.signatures)
-				bytes.write(signature);
+		for (byte[] signature : this.signatures)
+			bytes.write(signature);
 
-			return bytes.toByteArray();
-		} catch (IOException e) {
-			return null;
-		}
+		return bytes.toByteArray();
 	}
 
 }

src/test/java/org/qortal/test/network/OnlineAccountsTests.java

@@ -29,7 +29,7 @@ public class OnlineAccountsTests {
 
 
     @Test
-    public void testGetOnlineAccountsV2() throws Message.MessageException {
+    public void testGetOnlineAccountsV2() throws MessageException {
         List<OnlineAccountData> onlineAccountsOut = generateOnlineAccounts(false);
 
         Message messageOut = new GetOnlineAccountsV2Message(onlineAccountsOut);
@@ -58,7 +58,7 @@ public class OnlineAccountsTests {
     }
 
     @Test
-    public void testOnlineAccountsV2() throws Message.MessageException {
+    public void testOnlineAccountsV2() throws MessageException {
         List<OnlineAccountData> onlineAccountsOut = generateOnlineAccounts(true);
 
         Message messageOut = new OnlineAccountsV2Message(onlineAccountsOut);